Update phpunit/phpunit requirement from ~5.5 to ~7.5

[dependabot-preview[bot]]

Updates the requirements on phpunit/phpunit to permit the latest version.

Changelog

Sourced from phpunit/phpunit's changelog.

[7.5.20] - 2020-01-08

Removed

• eval-stdin.php has been removed, it was not used anymore since PHPUnit 7.2.7

[7.5.19] - 2020-01-06

Changed

• eval-stdin.php can now only be executed with cli and phpdbg

[7.5.18] - 2019-12-06

Fixed

• Fixed #3967: Cannot double interface that extends interface that extends \Throwable
• Fixed #3968: Test class run in a separate PHP process are passing when exit called inside

[7.5.17] - 2019-10-28

Fixed

• Fixed #3727: Problem hidden by PHPUnit's error handler
• Fixed #3863: \Countable needs to be checked before \EmptyIterator

[7.5.16] - 2019-09-14

Fixed

• Fixed #3801: Class constant as default parameter is undefined
• Fixed #3834: Trailing slash breaks code coverage on Windows

[7.5.15] - 2019-08-21

Changed

• Implemented #3765: Use ReflectionType::getName() instead of ReflectionType::__toString() (which is deprecated in PHP 7.4)

[7.5.14] - 2019-07-15

Fixed

• Fixed #3743: EmptyIterator instances are not handled correctly by Count and IsEmpty constraints

[7.5.13] - 2019-06-19

Fixed

• Fixed #3722: getObjectForTrait() does not work for traits that declare a constructor

Commits

• 9467db4 Prepare release
• 0f609d2 Delete eval-stdin.php
• 4263f76 Prepare release
• 2076dc7 Enhancement: Use actions/checkout@v2
• 6aab040 Lets waste three more characters on a solution for a problem that should not ...
• 33585d9 Hopefully prevent execution of this script in a webserver context.
• 7a46cf1 Fix: Avoid using master for GitHub actions
• fcf6c4b Prepare release
• 2902560 Update ChangeLog
• 773be5e Ignore .psalm directory on PHPUnit 7.5 branch
• Additional commits viewable in compare view

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